Intermittent inductive train control system



v Sept. 22, 1931. c. s. BUSHNELL 1,824,118

INTERMITTENT INDUCTIVE TRAIN CONTROL SYSTEM Filed Oct. 19. 1929 3 Sheets-Sheet. l

BY ea'%. ?iiw- I .6- M H n.

" p 1931- c. s. BUSHNELL INTERMITTENT INDUCTIVE TRAIN CONTROL SYSTEM Filed Oct. 19, 1929 3 Sheets-Sheet 2 BY M 4 ,ATTORNIE Sept. 22, 1931. c. s. BUSHNELL 1,824,118

INTERMITTENT INDUCTIVE TRAIN CONTROL SYSTEM Filed Oct. 19, 1929 s Sheets-Sheet a BY g' iaw [Z ATTQRNE Y Patented Sept. 22, 1931 ouiren STATES PATENT OFFICE OIELARIJES S. BUSHNELL, OF ROCHESTER, .NEW YORK, ,ASSIGNOB L D GENERAL RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK INTERMITTENT 'INDUCTIVE TRAIN CONTROL SYSTEM Application filed Gctober 19, 1929. Serial No. 400,867.

This invention relates to automatic train control systems, and more particularly {to ,asystem of the intermittent inductive type designed for use on railroads of the electric propulsion type.

.in the application of intermittent inductive train control to railway systems of the electric propulsion type, it has been experienced that a sudden change in the aprqpnh io sion current where this propulsion current is direct current, or an exceptionally large curv rent flow in :the track :rails and third rail where .the propulsion current is alternating in character, afiects the inductive receiving 1-; train control apparatus, and :at times causes .a false and unauthorized vbrake application.

in accordance with the present invention it is proposed to so organize the receiving coils of the car-carried apparatus that the induc- 20 tion of voltage in the receiving apparatus is neutralized, this preferably being obtained by employing two receiving coils so connected in series that the induction of voltage therein due .to propulsion current ,flowing in the track rails, the third rail or Wires parallel thereto, are equal and opposite.

Gther objects purposes :and characteristic features of the invention reside in the 1 I10- vision of car-carried apparatus appl icah e to to electric locomotives in which a controller and engineers brake valve is located ateach end of the electric locomotive, which includes :two separate receive-rs located on opposite sides :of the locomotive the proper one of which is out into service when the brake valve and controller handles at a particular end or" the locomotive are be'ing used.

ther objects, purposes and characteristic features of: the invention will in pafrt bQ'dbVlone from the accompanying drawings and will in part be described hereinafter.

In describing the invention in detail reierehoe will he made to the accompanying drawings in which Fig. 1 shows in a conventionalmanner'the car-carried and trackway apparatus [of one system embodying the present invention;

Fig. :2 shows an enlarged side Vl13W-Qfltil'lB receivers shown in .Eig. 1 lot :the drawings;

,Fig. .3 shows the core and coil structure of the receiver shown in Fig. 12;; and

Fig. 4 shows the :aclmovvlcdging apparatus of a system otherwise theisamc as that shown Fig. 1 of the drawings.

Referring to .Figl o the drawings, th embodiment of the invention illustratcdiha been shown applied to a railway system ha ing track rails 35 divided by insula ing joints 6, into blocks, at the entrance to ea h o "which is located a signal 78., and of whic system :for convenience, a portion of the sblccks J and K only have been shown. Although these lilockszare insulated ifrcm- 8213 1. other by insula ing J'Qillis fihese' blocks are elec trically connected fo ape/Imit- :flow of direct propulsion curren Jay th balanced impedance :bcnds B,;asshcrvn. At the entrance to each block and just in the rear .o-fthe signal S is located an induct comprising a core 5? construct d of mated magnetic material and :having a e09jl B on the back yoke thereof, this cell 18 being closed in a circuit of low resistance cinder clear :tlaflic conditions as conventionally 15 shown by the contacts ,9 and .10 of the polar neutral line relay v"LR.

The electric locomotive -.on which the calcarried apparatus is'mounted has beenccmventionally illustrated by {the wheels and axles .12. In the front cab of the electric locomotive is provided the usual .engineers :brake valve and controller (not shown), .a whistle valve Wt, and a cut-1m device GD including the lever L 111 :the :rear .cab is provided similar apparatus which includes the whistle valve and the cutsin device @193. In this connection :it may be pointed" out :that the cut-win devices CD and Cl?) and :contacts associated therewith function an a manner more particularly described in the operation =OI the system heneinaifiter, and also includes halves so organized that the device iis :cut-out of service pneumatically :unless one ofthe cut-in devices (3D :or CD is in'itscut-in :(namelythe :No. L) position.

The car-carried apparatus also includes the relays R R :and R amacknowledding stick relay Aspen aclmowlledging relay 36R audio time element-relay TR. iEhecar-car- #100 ried apparatus also includes a ballast lamp BL, two acknowledging push buttons A070 and A0762, and a reset push button RS only accessible from the ground. In order to more clearly understand the particular embodiment of the invention illustrated it is deemed'expedient to consider'the operation of the system.

0peratz'0n. With the car-carried apparatus in its normal clear position, as it would be after having been reset by operation of the reset push button RS, the primary coil P is energized through the following circuit z-beginning at the terminal B of a suitable car battery, wire 15, primary coil P wires 16 and 17, contact 18 of the cut-in switch CD wire 19, contact 20 of the cut-in switch CD wires 21 and 22, ballast lamp BL, wire 23, winding of the relay to the other terminal C of said car battery. The flow of current in this circuit maintains the relay energized, this relay R serving as a check relay for indicating the low of an ade iate amount of current in the primary coil 1 to assure functioning of the system, and also serving as a resistance unit for obtaining a voltage (the resistance drop over this relay) for maintaining the low voltage control relay R energized. I

It may be pointed out that the ballast lamp BL conventionallyrepresents suitable means for maintaining the current flowing in the primary coil P constant and at a definite value irrespective of fluctuation of battery voltage. This unit BLmay be a lamp having a very high positive temperature e o-efficient of resistance, so'that a slight increase of current flow therein will increase the temperature and therefore the resistance to an extent to limit such current flow. This unit BL, on the other hand, may be an electrically operated changeable resistance, such as a carbon pile operated by. an electromagnet.

which produces a similar effect.

l/Vith the relay R energized there is a small potential drop over the winding of this relay R and this potential drop is applied -t0 the relay B through the following cir- 'cuit :beginning at the plus side of the relay R wires 23, 24, and 25, coils S of the right hand receiver RR, wires 26 and 27, contact 28 of the cut-in device CD wires 29 and 30, winding of the relay R, wires 31 and 32, front contact 33 of the relay R to the terminal C of the car battery. The flow of the current in this circuit will maintain the relay R energized and by reason of closure of its front contact 33 will maintain the relay R energized through the following circuit:. beginning at the terminal B of said car battery, wire 35, front contact 36 of the relay R wire 37, winding of the relay R wire 38, contact 33 of the relay R to the other terminal C. of the car battery. i

With the relay R energized the acknowledging relay AS (picked up in a manner explained hereinafter) is maintained energized through the following circuit :beginning at the terminal B of the car battery, front contact of the relay R wires 40 and 41, front contact 42 of the relay AS, wire 44, the lower winding 43 of this relay to the other terminal C of the car battery. It is thus seen that the relay AS is held energized by the relay R that the relay R is held energized by a circuit includ ing a front contact of the relay R and that the relay R derives its energy from the potential drop across the relay R Under these conditions of the relays, the electropneumatic brake applying valve EPV is energized through the following circuit beginning at the terminal B, back contacts 45 of the acknowledging relay AcR, wires 46 and 47, front contacts 48 of the relay R wire 50, front contact 51 of the acknowledging relay AS, wire 52, winding of the valve EPV, to the other terminal 0 of the car battery. 7 V

Let us now assume that the car 12 is travelling from left to right in the block: J, and that the coil 8 of the track inductor I is open circuited, because the line relay LR is either energized to its left hand position or is deenergized. As the car 12 passes the inductor I the right hand receiver RR cooperates with the inductor I, and during its passage over this inductor produces an increase of flux through the secondary coils S the turns in the coils S being in such a direction that the voltage induced in these coils S due to this increase in flux opposes the voltage normally applied to the control relay R so that theenergizing current for the relay R falls to such a value that its contacts 33 will open. It is of course understood that a voltage of the opposite polarity will be induced in the secondary coils S as the receiver RR leaves the inductor. This second wave of the induced voltage is however of no importance in that if the relay R has dropped, its energizing circuit including its stick contact is broken. Since the relay R is a stick relay the opening of its stick contact 33 will prevent picking up of thisrelay when the induced voltage ceases.

Let us first assume that the engineer was alert and has in the mean time depressed his acknowledging push button Ack Drop ping ofthe relay R effects deenergization of the relay R and as this relay R assumes its retracted position the relay R is permitted to again pick up through the following circuit :beginning at the plus side of the winding relay R wires 23, 24 and 25, secondary winding S, wires 26 and 27, contact 28 of the cut-in device CD wires 29 and 30, winding of the relay R wires 31' and 55, back contacts 56 of the relay R wire 57, to common return wire .AcR, wires 60, l0 and 37, winding of the relay R wire 38, front contact 83 of the relay R to common return wire C connected to the other side of the car battery.

The relay R is thus returned to its nor- 'mal energized .position,'hecause the engineer has manifested his vigilance and has maintained the acknowledging relay AGiR energized through the following circuit:- beginning at the terminal B of the car battery, wire :61, winding of the relay AGE, wire 62, winding 63 of the relay TR, wires 64, 65 and 66, acknowledging push button A670 to common return wire C and .a grounded part of the car, such as the truck, as conventionally illustrated. :shouid be noted that the device EPV relies for its current flow on a circuit through either the back contact 45 of the relay AcR or through wire 67, contact 68 of relay TB and wire 69. It is thus apparent that the engineer must operate his push button A016 to energize the relay A03 for a very short time only while passing over the inductor I, because this depression of the push button A010 also causes heat to be generated by the coil 63 of relay TR, which heating opens the circuit for the device EPV at the contacts 68 of the thermal relay TR, if the engineer pushes the acknowledging button A076 too long. The acknowledging apparatus is thus protected against misuse, such as permanent tying down.

It has just been explained how the relay R is returned to its normal attracted posi- .tion. Attention is now directed to the fact that during the time that the relay R is in its deenergized position with the relay AcR in its energized position and the push button Ade depressed the audible whistle is sounded through the following circuit beginning :at the terminal B, front contact 15 of the relay AcR, wires 60 and &0, contact 36 of the relay R in its retracted position, wire 70., contact 71 of the cut-in device CD wire 72, winding of the whistle valve it, which is sounded while this winding is energized, wires 73 and 66, through the push button A070 to common return wire C. The sounding .of the whistle YV attracts the attention .of the fire-man, so that the fireman is :aware of the fact that the train has passed by an inductor in its stop condition.

Let us now assume that during the passage of the '12 the inductor I the engineer has not been alert, but was incapaciitated .or asleep, :and let us observe what :efiect momentary dropping of the relay R will have .on the car-carried apparatus. Dropping of the relay R is only momentary in that it effect-s dropping of the" relay R which dropping of the relay R restores the relay R but this dropping of the relay 'R ailso 'efiiects deenergiL-ation and dropping of the relay A 8, in that the lower winding of the relay AS derives its enercurrent from the front contact $86 of the relay B through the medium of the wire Obviousiy, :de'energ-ization of the "relay- AS also eif'ects deenergization of the device EPV in that its energizing circuit thereof will be broken at the contact'ol. Dropping of the device .EPV will of course effect .a brake application which will bring the train to a stop.

Vith the relay once .assu ing its deenergized position it can not be restored unless the train is :brought to a stop and the reset push button BS is operated simultaneously with the operation of. one of the acknowledging push buttons A0761 or half. "The engineer must therefore alight to the ground and depress the push button RS while his fireman depresses the push button A016 thereby completing the following cir- :cuit;z-beginning at the terminal B of the car battery front contact 7 5 of the relay Aclhwire 76,1191132/1 winding 77 of the relay AS, wire 1'78, push button ZRS, wire 79 to a ground portion 'of the car, wire 73 push button contact .Aclc't, wire 74: .to the common return awicre Obviously with the relay AS restored to normal the car-carried apparatus can be brought back to its normal condition :in which :the .dewice .EPV is energized.

the reset push button BS is only accessible from the ground the engineer is penalized for his failure to operate the acknowledging @push button Ack :or A010 in time, that he must bring the :train to a stop, must :alight to the ground and must -cooperation with the fireman operate the push button RS simultaneously :with the firemans operation of the acknowledging .push button Act or Ack In this connection, if desired, ;a speed governor vmay be added which is driven from the axles of the vehicle and which is provided with :a contact closed only when the train is moving at a speed below, say two miles per hour, and this contact may be substituted for the reset contact RS. In this latter case the penalty resides the requirement of the engineer to bring the train substantially to ;a stop.

The contact 80 9f the cutin device GD -tion box 91.

the engineers cab and is of little importance insofar as the present invention is concerned.

Since the apparatus functions the same irrespective of which end of the locomotive leads, it is deemed unnecessary to describe the operation of the system with the cut-in device CD cut-in, and with the cut-in device CD cut-out.

One of the features of the present invention resides in the construction of the re ceivers RR and LR. It should. be noted that these receivers have a primary coil on the back yoke of the inverted U shaped core 83, and that this yoke is depressed in the middle (see Fig. 3 of the drawings), so as to form a very compact structure, which core and coils may be housed in a rather small non-magnetic metal housing (see Fig. 2- of the drawings). This nonmagnetic housing 84 is adjustably securec to large pins 85 projecting sidewise from the truck, by the provision of blocks 86 adapted to slide vertically on the brackets 87. These blocks 86 support the brackets 87 through the medium of threaded thrust pins 88 having lock nuts 89 thereon, and these thrust pins 88 are screw threaded into the brackets 87 Attention is also directed tothe. fact that the wires leading to the primary coil P and the secondary coils S pass through the conduit 90 into the junc- Attention is further directed to the fact that the magnetism passing through the primary coil P passes through the secondary coils S vertically in opposite directions, so that the turns in the secondary coils must be opposite, in order that the inductive effect due to a change in the magnetism derived from the primary coil P may be cumulative. For this reason, no inductive effect due to current flowing in wires or rails parallel to the track rails will be experienced in the secondary circuits, in that the magnetic lines will pass through the secondary coils S in such a direction that the voltages induced in thesesecondary coils S are opposite, and neutralized, in so far as they affect this secondary circuit. In other words. the flow of either alternating current or an abrupt change in the flow of direct current in the track rails, or in the third rail of the railway system, will not materially affect the flow of current in the secondary coils S and therefore the system embodying the present invention is such as to be immune to propulsion current.

Applicant has therefore shown one embodiment of his invention which is immune to propulsion current, and which embodies essential features for application of the system to an electric locomotive having a con troller and an air brake valve at each end thereof. Attention is again directed to the fact that the electro pneumatic valve EPV is pneumatically cut-in and capable of effecting a brake application only when either of the cut-in devices CD or CD is in its cut-in position. This electropneumatic valve EPV is of course one of the normally 7G energized type and is constructed to vent the brake pipe, and effect a brake application, when deenergized.

Modified c0nst*2'=ucti0n.-In Fig. 4 of the drawings have been shown acknowledgingfi push buttons A070 and A070, which may be substituted for the acknowledging push buttons A070 and A070 together with the thermal relay TR and the acknowledging relay Acft. In order to simplify the description of the system when modified to omit the time element thermal relay TR and the acknowledging relay AcR, the wires leading from the apparatus of Fig. 4 of the drawings have been numbered exactlythe same as the corresponding wires 111 the complete system shown in Fig. 1 of the drawings. The modified construction shown in F ig. & obtains the same results as does the corresponding apparatus as shown in be Fig. l, and in order to bring out this functioning of the apparatus, only the similarities between the two structures will be pointed out.

Referring to Fig. 1 it will be noted that os the contact 68 removes the terminal B from the wire 47 only af er an interval of delay after one of the push buttons A070 and A070 have been depressed. Similarly, the terminal B is removed from the wire st? in Fig. 4 of'the drawings only after an interval of delay'after depression of one of the push buttons AcL or Adz, because the normally closed contacts 93 and 96 have their opening retarded by dash pots 97 and 98, these con er tacts being urged to their open position by tensioned springs 99 and 100. Similarly, the wires 60 and 76 in Fig. 1 are connected to the terminal B immediately upon depression of the push buttons A070 or A070 in "11c Fig. l of the drawings, as is also true in Fig. 4 of the drawings, where depression of the push buttons Acir or A070 closes the contacts l0l-l02 or lO3-l04, respectively. Similarly wires 73 and 73 are connected IS to ground during acknowledgement in Fig.

4 of the drawings, as is also true of Fig. 1.

Having thus shown and described one rather sp cific embodiment of the present invention and having shown one way iii- 6 which the invention may be modified, it is desired to be understood that the particular circuit arrangement and devices selected have been selected for the purpose of facilitating description of the invention, rath or than its scope or the exact construction preferably employed in practicing the same, and that various changes, modifications and additions may be made to adapt the inven-.

tion to the particular system or locomotive to which the invention to: be applied, all without departing fromv the spirit. or scope: of the invention or the idea at means; underlying the same, except. as: demanded by the scope of the following claims.

What I claim; as new is 1. Train control. ap-caratus immune.- to! the flow oi propulsion current comprising; a re.- ceiv r consisting: 0t. 21 primary coil on the: bacl eke of an inverted U-shaped core; a secondary coil on: each; leg; said secondary coils being connected in seriesw so that a changeof flux in said corewillproduce volts ages in said secondary coils which are cumulative; an energizing circuit for said primary coil including source of direct cur.- rent and. a check, relay; a controlrelay hav-- a stick contact a secondary circuit cluding in series: said control. relay, its stick contact, said secondary coil and said check.

relay; and trackway means tor changing the reluctance of the magnetic circuit including: said core; whereby the voltage drop oversaid check relay serves as a source of current to: maintain said control relay.

energized, and whereby propulsion currents cannot induce a voltage in said secondary circuit. i

2.. Train control. apparatus immune to the flow oi propulsion current comprising; a re-- ceiver consisting of a primary coil on the back yoke; of an inverted U-shiapedcore disposed lengthwise: of the train; a secondary coil on each leg, said. secondary coils being connected in series so. that a change of flux in said core will produce voltages in saidsecondary coils which. are cumulative; an energizing circuit tor said primary coil in.- cluding a source of direct. current and a .check relay a control relay having, a stick.

contact: a secondary circuit including; in series said control relay, its stick circuit, said secondary coils and said check relay; and trackway means for changing thereluctance of the magnetic circuit including said core; whereby the voltage drop. over said check relay serves as a source of current to maintain said control relay energized, and whereby propulsion currents flowing in conductors:

"substantially parallel to the: track rails 7 including a. series said control relay, its, stick con-tact, said seccndarycoils. and said check relay and an inductor at the entrance to, each block located. so as to; magnetically cooperate with said receiver upon passage oi the; car carrying said apparatus consisting of a core of iron when in its; active condilZlQll; v

4:, Train control apparatus immune to the flow oi propulsion current comprising a. re: ceiver consisting of a primary (2011 on the.

back yoke of, an inverted U'-shaped,- core; a secondary 0011 on each leg; said secondary coils.- being connected 111 series so that a change of flux in said core will produce voltages in said secondary coils which, orecumulative; an energizing circuit for said pri mary coil including a sourcev of direct current and a. check relay; a. control relay ha I ing a stick contact; a secondary circuit 1 cluding-in seriesv said control relay, its stick contact, said secondary coils and said check relay; and an inductor at the entrance to. each. block located so as to. magnetically cor operate; with said receiver upon passage. of

the. car carrying said apparatus, consisting ofa core ofiron when in its active condition,

and a: coil. on said inductor core closed in a circuit oflow resistance under: clear traflic. conditions, i

5. Car-carried apparatus. for automatic train control systems comprising an inductive vehicle carried receiver including a primary winding and a secondary winding;

a source of. direct. current; a check relay; a circuit including said check relay, said primary coil and said source in series; a COIL. trol relay connected in series with said second'ary winding and across, said check relay, so that the 'voltage drop. over said; check re.- lay serves as. a source of current for said control relay; a. repeater relay controlled. by said control: relay an acknowledging relay having a. stick. contact; a stick circuit for.

said acknowledging relay including. said last mentioned stick contact and. a trout contact of said repeater relay; a normally energized electrically operated brake controlling valve. which if de-energized applies. the. brakes of the vehicle; and a circuit for energizing said valve including front contacts of said check relay and front contacts of said repeater relay in series. I

6. Car-carried apparatus for automatic train control systems comprising; an induc tive vehicle carried receiver including a} primary winding and a secondary winding;- a source of direct current; a check relay; a circuit including said check relay, sa d .primarycoil and said source in series; a control relay connected in. series with said sec ondary winding and across said check re.-

'lay, .so that the voltage drop over said check relay serves as a source of current; for said control relay; a repeater relay controlled by said control relay; an acknowledging relay having a stick contact; a stick circuit for said acknowledging relay including said last unentioned stick contact and a front of said "repeater relay; an auxiliary circuit for said acknowledging relay including a manually controllable contact, a normally energized electrically operated brake controlling valve which if de-energized applies the brakes of g'train control systems comprising; an inductive vehicle carried. receiver including a primary winding and a secondary winding; a source of dlrect current; a check relay; a

circuit including said check relay, said primary coil and said source in series; a

control relay connected in series with said secondary winding and across said check relay, so that the voltage drop over said check relay serves as a source of current for said control relay; a repeater relay controlled by said control relay; an acknowledging relay having a stick contact; .a stick circuit for said acknowledging relay including said last mentioned stick contact and a front of said repeater relay; an auxiliary circuit for said acknowledging relay including a manually controllable contact; a normally energized electrically operated brake controlling valve which if deenergized applies the brakes of the vehicle; and a circuit for energizingsaid valve including front contacts of said check relay and said repeater relay in series and contacts which are opened if said manually controllable contacts are kept closed for more than a predetermined time.

8. Car-carried apparatus for automatic train control systems comprising; an inductive vehicle carried receiver including. a primary winding and a secondary winding; a source of direct current; a check relay; a circuit including said check relay, said primary coil and said source in series; a control relay connected in series with said secondary winding and across said check relay, so that the voltage drop over said check relay serves as a source of current for the circuit including said control relay and said secondary coil in series; a repeater relay controlled by said control relay; an acknowledgingrelay having stick contacts; a stick circuit for said acknowledging relay includingsaid last mentioned stick contacts and front contacts of said repeater relay; a normally energized electrically operated brake controlling valve which if deenergized applies the brakes of the vehicle; and a circuit for energizing said valve including front contacts of said check relay and front contacts of said repeater relay in series, and an audible signal sounded upon deenergization of said repeater relay.

9. Oar-carried apparatus for automatic train control systems comprising; an inductive vehicle carried receiver including a pri mary Winding and a secondary winding; a source of direct current; a check relay; a circuit including said check relay, said primary coil and said source in series; a control relay connected in series with said secondary winding and across said check relay, so that the voltage drop over said check relay serves as a source of current for said control relay; a repeater relay controlled by said control relay; an acknowledging relay having stick contacts; a stick circuit for said aknowledging relay including said last mentioned stick contacts and a front of said repeater relay; an auxiliary circuit for said acknowledging relay including a manually controllable contact; a normally energized electrically operated brake controlling valve which if deenergized applies the brakes of the vehicle; and acircuit for energizing said valve including front contacts of said check relay and said repeater relay connected in series, and an electrically operated audible signal sounded momentarily and only when said manually controllable contacts are closed and said receiver passes an active inductor.

10. Car-carried apparatus for automatic train control systems comprising; an inductive vehicle carried receiver including a primary winding and a secondary winding; a source of direct current; a check relay; a circuit including said check relay, saidprimary coil and said source in series; a control relay connected in series with said secondary winding and across said check relay, so that the voltage drop over said check relay serves as a source of current for said control relay; a repeater relay controlledby said control relay; an acknowledging relay having stick contacts; a stick circuit for said acknowledging relay including said last mentioned stick contacts and a front contact of said repeater relay; an auxiliary circuit for said acknowledging relay including manually controllable contacts, means for deenergizing said electrically operated valve if said manually controllable contacts are kept closed for more than a predetermined time; a normally energized electrically operated brake controlling valve which if de-energized applies the brakes of the vehicle; and a circuit for energizing said valve including front contacts of said check relay and said repeater relay in series, an electrically operated audible signal sounded momentarily and only when said manually controllable contacts are closed and said receiver passes an active inductor.

11. Car-carried apparatus for automatic train control systems comprising; an electropneumatic Valve normally energized and which if de-energized applies the brakes of the train; means controlled from the trackway for eifecting de-energization of said valve and effective for a time only; and acknowledging means for preventing deenergization of said valve and protected against misuse comprising; two normally deenergized relays the first of which is quick acting and the second of which is slow acting, a back contact of said slow acting relay included in series with the circuit of said valve, a front contact of said quick-acting relay for completing an auxiliary circuit for maintaining said electro-pneumatic valve energized irrespective of its control from the trackway, and an energizing circuit for said two relays including a manually operable contact.

12. Train control apparatus immune to the flow of propulsion current comprising; areceiver consisting of a primary coil on the back yoke of an inverted U-SllilPQd core; a secondary coil on each leg; said secondary coils being connected in series so that a change of flux in said core will produce voltages in said secondary coils which are cumulative and so that equal vertical flux changes in the two legs will induce equal and opposite voltages in said secondary coils in series, a normally energized stick brake control device controlled by said secondary coils which if once deenergized remains deenergized until specially restored manually operable means which if actuated prevents deenergization of said device in spite of its control by said secondary coils, and means for protecting said manually operable means against misuse.

13. Car-carried apparatus for automatic train control systems comprising; an electropneumatic valve normally energized and which if de-energized applies the brakes of the train; means controlled from the trackway for effecting de-energization of said valve and effective for a time only; and acknowledging means for preventing deener giza-tion of said valve and protected against misuse comprising; two normally deenergized relays the first of which is quick acting and the second of which is thermally operated, a back contact of said thermally operated relay included in series with the circuit of said valve, a front contact of said quick-acting relay for completing an auxiliary circuit for maintaining said electropneuma-tic valve energized irrespective of its control from the trackwa-y, and an energizing circuit for said two relays including a manually operable contact.

In testimony whereof I afiix my signature.

CHARLES S. BUSHNELL. 

